It is well known to those skilled in the art that aluminum (primary or secondary) can be decontaminated by treating melts thereof with chlorine. In this regard, chlorine gas is bubbled up through the melt to strip the melt of such contaminants as hydrogen, magnesium, sodium, calcium, fine oxides, etc. The chlorine may be introduced as 100% chlorine gas; diluted (e.g. with inert gas) chlorine gas; or may be released from a variety of gaseous or solid materials such as Freon 12, hexachloroethane, chloronated hydrocarbons, etc. which decompose in the melt. Such chlorination treatments are performed at temperatures typically ranging from about 675.degree. C. to about 900.degree. C. and in some instances are conducted under a layer of molten flux floating atop the melt to protect the melt from ambient air oxidation. During the course of the treatment, hydrogen and the fine oxides are removed primarily by mechanical action while the magnesium, sodium, and calcium, are removed by chemical reaction with the chlorine to form magnesium chloride, sodium chloride and calcium chloride which floats to the top of the melt and are skimmed off. Unfortunately, unreacted chlorine and gaseous aluminum chloride are evolved from the melt. Upon contact with moisture in the air, the aluminum chloride forms HCl and fine aluminum oxide powder. This hydrogen chloride, fine aluminum oxide and excess chlorine pollutes the surrounding atmosphere and necessitates the costly purchase, operation and maintenance of air treatment equipment to remove the pollutants.
It is the primary object of the present invention to substantially eliminate chlorine/chloride offgassing from aluminum melts undergoing chlorination by blanketing the melt with a molten layer of flux which not only protects the melt from ambient air oxidation but also consumes the chlorine/chloride offgases from the melt before they pollute the surrounding environment. This and other objects and advantages of the present invention will become more readily apparent from the description thereof which follows.